Substitution of fish meal by Tenebrio molitor meal in the diet of Dicentrarchus labrax juveniles

The aim of the study was to evaluate the effect of the inclusion of Tenebrio molitor meal (TM) - as an alternative protein source in practical diets - on growth and feed efficiency of European Sea Bass (Dicentrarchus labrax) juveniles. Three experimental diets were prepared by replacing fish meal by graded levels of TM (TM 0%, TM 25% and TM 50%). All diets were isonitrogenous (CP 54.6% on wet basis) and isocaloric (22 MJ kg-1). Four hundred and fifty sea bass juveniles of 5.23±0.82 g (initial body weight ± sd) were individually weighed and randomly distributed in 9 circular fiber glass tanks (500l) supplied by borehole sea water. The water temperature ranged between 19-20oC. Each diet was assigned to triplicate groups of 50 fish and feed was distributed to apparent satiation by hand, twice a day for 7 days per week. All feed was consumed by fish without feed loss. At the end of the feeding trial, the performance traits of weight gain, specific growth rate, feed conversion ratio and feed consumption were evaluated. The diets and the whole body composition of ten pooled fish per replicate group were analysed for proximate composition, gross energy and fatty acid composition. The results showed that up to 25%, the inclusion of TM meal in diet did not lead to adverse effects on weight gain, while at 50% level, TM induced growth reduction and less favourable outcomes for both specific growth rate and feed consumption ratio. Protein efficiency ratio and feed consumption were not affected by the inclusion of TM. The whole body proximate composition analysis did not show any differences between treatments. On the other hand, TM inclusion influenced the fatty acid composition of body lipids. In particular, a decrease in the contents of EPA (from 395.07 to 164.10mg/100 g) and DHA (from 619.88 to 203.26 mg/100 g) were observed with the increase of the inclusion to 50% TM.